Fix `compactify` scripted test failure.

Travis CI stopped allowing long file names on its file system. We need
to explicitly set lower limit on file name length using
`-Xmax-classfile-name` Scala compiler option. We set the limit to 240
characters.

Fixes #1553
Merge pull request #1557 from gkossakowski/scripted-compactify

Fix `compactify` scripted test failure.
Merge https://github.com/sbt/sbt into 0.13
correct comments